1. Field of the Invention
The present invention relates to hydraulic pistons and actuation apparatuses.
2. Background Information
Hydraulic piston and cylinder assemblies are used in almost countless contexts.
In certain situations, a series of hydraulic units are used to achieve a mechanical result which is not achievable through use of a single hydraulic unit. One example of such an arrangement is that of the stabilizing hydraulic boom assembly as used for portable cranes, xe2x80x9ccherry pickersxe2x80x9d, ladder trucks for fire departments, etc. Such hydraulic boom assemblies presently include at least one hydraulic unit which is oriented for extending the boom assembly horizontally away from the vehicle, and a second hydraulic unit which is oriented vertically for raising and lowering ground-contacting pads or feet.
Presently, in this, and any other such multi-hydraulic unit system, each hydraulic unit requires its own hydraulic fluid circuit and actuation mechanisms (switches, valves, etc.). This can often involve considerable lengths of telescopic conduit and hoses, and, if such could be avoided as through application of the present invention, considerable duplication of expense for redundant actuators, valves, switches, etc. As with any mechanical system, the multiplying of components likewise multiplies the opportunities for mechanical failure or malfunction. In addition, the presence of exposed conduits and hoses over considerable lengths increases the likelihood of breach thereof and accompanying hydraulic system failures. This is particularly true with respect to exteriorly positioned, exposed telescopic conduits (xe2x80x9ctrombone tubesxe2x80x9d) which are particularly susceptible to damage and seal problems arising from particulate (dirt) contamination.
Providing a serial hydraulic unit system which obviates requirements for a number of independent hydraulic circuits and associated actuation systems equal to the number of hydraulic units would, at a minimum, reduce costs and hydraulic system complexities and, as will be discussed below, actually provide certain safety benefits when used in certain contexts. Further eliminating external, telescopic conduits for hydraulically feeding remote hydraulic cylinder units would eliminate many mechanical problems and associated costs.
It would be further beneficial to users of multiple hydraulic unit systems to provide such a system which, without requiring multiple, independent actuation systems, could be configured for extending and/or retracting hydraulic units in certain prescribed sequences.
Each of these objectives are left unsatisfied in the present art.
In view of the foregoing, it is an object of the present invention to provide an improved multiple hydraulic unit system.
It is another object of the present invention to provide an improved multiple hydraulic unit system which, when compared with conventional such systems, requires fewer components.
It is another object of the present invention to provide an improved multiple hydraulic unit system, each constituent hydraulic unit of which shares at least part of a hydraulic fluid circuit with another hydraulic unit in the same system.
It is another object of the present invention to provide an improved multiple hydraulic unit system, all constituent hydraulic units of which are assured to extend and/or retract upon completed actuation of the system.
It is another object of the present invention to provide an improved multiple hydraulic unit system, constituent hydraulic units of which extend and/or retract in a predetermined sequence.
It is another object of the present invention to provide an improved multiple hydraulic unit system, constituent hydraulic units of which extend and/or retract in a predetermined sequence, without requiring the outside actuation of separate control mechanisms for each such hydraulic unit.
It is another object of the present invention to provide an improved design for a multiple hydraulic unit system which involves a portion of the conduits thereof residing within, and extending through one or more of the constituent hydraulic unit cylinders, as opposed to residing outside of such cylinders to thereby be exposed to damage and/or environmental degradation.
In satisfaction of these and related objects, the present invention provides an serial, multi-unit hydraulic system which, though multiple hydraulic units (piston and cylinder assemblies) are actuated during any single operation of the system, uses merely a single hydraulic fluid circuit for extending and retracting all constituent hydraulic units. The incorporation and arrangement of certain control valves effects a prescribed sequence of extension and retraction of the constituent hydraulic units, without involving separate, external control apparatuses. The unique design of the present system involves the enclosure of certain conduits within hydraulic cylinders, which conduits would ordinarily reside outside of cylinders, exposed to potential damage and in environmental degradation.
Normal actuation of a serial, multi-unit hydraulic system of the present invention assuredly results in the full extension or retraction of all constituent hydraulic units. This is the result of the sharing of hydraulic fluid circuits between the constituent hydraulic units, and can provide significant safety dividends when such a system is used in certain contexts. For example, when a system of the present invention is used in the context of a lateral support boom assembly for a portable crane, or similar application, it is assured, upon proper operation of the system, that both the horizontal or vertical hydraulic units will extend and retract, thereby insuring that proper support it is provided during extension, and inadvertent entanglement with ground surfaces, surrounding structures, etc. will be avoided when the boom is intended to be fully retracted.
Furthermore, through use of certain integral pressure (control) valve arrangements, as will be described in more detail later herein, individual hydraulic units residing in systems of the present invention can be made to extend or retract in predetermined sequences, rather than as a result of separate actuation of independent, hydraulic unit-specific control systems. Again, using the example of a lateral support boom assembly, this can be quite beneficial in assuring, for example, that the horizontal hydraulic unit will first extend, followed by the vertical hydraulic unit, whereas. upon retraction, the vertical hydraulic unit will retract first, followed by he horizontal unit. Any reflection upon proper operation of a lateral support boom assembly will reveal the significance of such an operation, and the benefits of achieving such operation without requiring multiple, independent control mechanisms.
A core achievement of the present invention is the actuation and sequential control of a remote hydraulic unit despite such unit""s sharing of a common hydraulic fluid circuit with an intermediate hydraulic unit in a serial arrangement. In addition, the elimination of external conduits as would otherwise be required for operating such a remote hydraulic unit, as made possible by the presently presented design, provides considerable advantages in system longevity and reduction in component redundancy.